Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: mingom on January 20, 2014, 06:38:59 PM
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Hey guys,
Went out to check the boiler tonight, checked the water when I was out there - no issues, but I can hear a bubbling or gurgling noise - temp was only at 176-178, has only gone up to 185 recently so I'm not sure it boiling - has anyone heard this before?
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I hear it every time my boiler fires.
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Water boiling. I've played around with switching the pipe connections, running at a lower temp and running two pumps for more flow but I still get it. I am used to it now.
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mingom
I have a port/main owf, all of the sudden I heard same noise coming in at return line and bubbling up from bottom to the top.
I was able to see return and supply line in the basement and could see air going back on return but not on supply. long story short, I had a drain valve that went bad and was sucking air on return side after exchanger, plumber said it happens occasionally. I caulked up and it went away. will replace in the spring.
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mingom
I have a port/main owf, all of the sudden I heard same noise coming in at return line and bubbling up from bottom to the top.
I was able to see return and supply line in the basement and could see air going back on return but not on supply. long story short, I had a drain valve that went bad and was sucking air on return side after exchanger, plumber said it happens occasionally. I caulked up and it went away. will replace in the spring.
Do you have the pump on the return side pulling the water?
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Good catch and good post Willowbk
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Been awhile, been monitoring it a bit... Think it's just boiling but it's weird- it can happen from170ish on up if there's a roaring fire. Just sounds like the whole tank is rumbling/boiling.
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I've heard a gurgle or two if air has somehow gotten in the lines. With a blazing fire it sounds more like when you're heating a pan of water on the stove, a sizzle actually.
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mingom
I have a port/main owf, all of the sudden I heard same noise coming in at return line and bubbling up from bottom to the top.
I was able to see return and supply line in the basement and could see air going back on return but not on supply. long story short, I had a drain valve that went bad and was sucking air on return side after exchanger, plumber said it happens occasionally. I caulked up and it went away. will replace in the spring.
Do you have the pump on the return side pulling the water?
What side should the pump be on? With the house on the pressure or suction side?
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I normally install the circ on the supply to the house side and as I have posted before I bring the return back to the hottest portion of the boiler, conventionals to the top and gassers to the bottom, I think this helps to stabilize the temps in the boiler.
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My pump supplys to the house - on the lower side of the boiler, return on the top. Its not air in the lines or anything like that -it only happens when it gets hot (generally 175+) but have heard it down to 170. It only seems to happen when the fire is really ripping inside.
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Water level is up? you are boiling your water and this is not good for the boiler, can you increase the water flow, larger circulator or if it's 3 speed try running it on high.
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Water level is good - just checked. Bumped the 3 speed grunpfos up to high - I'll see what happens with that.
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My 4400 does the same thing - Like you said, only when the fire is cooking good - It seems the sound is close to the front of unit - I think it is just a hot spot , where the fire is licking the side wall intensely in one location causing the water to boil, just in one spot.
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Hey what does that mean when water is boiling below 212 degrees. How can that be? Systems sucking air into the pipes?
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I think my boiling is coming from the water tubes going through the chamber. I am assuming the flow is not enough to prevent the boiling. I've thought about adding a second pump to run when it's on a burn using the extra bungs but need to drain it down. I should have put some valves on last year when I drained it.
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Is it possible that IF the wood is loaded at the front of the stove the water could be much hotter in that area?
Where is the temp sensor on your furnaces?
When I load mine I keep the wood close to the door to keep the flame and heat ahead of the baffle in the back of the box. When the temp reads over 193/4 ( sensor is mounted at the rear of the furnace ) I can hear it bubbling. So to me either the temp sensor is not accurate or the water is hotter at the front than at the back? I dunno?
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Sensor is in the back, maybe I've been loading too close to the front?
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Pressure is what effects boiling point. Like nascar radiators running 56psi and running 280 degree temps with no boiling. Thus the dumb rule on stat limits
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Thanks Sprinter - i understand the pv=mrt rule, but i'm not quite understanding what you're saying about my boiler. It's not pressurized so it should always be equal due to being open to atmosphere correct?
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I think we are talking non pressurized systems here and I am sure you know that. I just think when I have a 150 gallon water jacket and a pump doing 7 gpm there is a chance of a hot spot.
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Alright - a little perplexed - went out this AM, temp was low (155)- had eaten through all the wood I had loaded (-8 outside). I got it roaring again pretty quick, but again - boiling noise but way down at 156. It must be creating hot spots??
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Mingom, try cutting the air back a bit for a slower burn, constantly boiling water anywhere in your boiler is bad for the boiler.
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Sounds good - just can't figure out why it started doing it all of the sudden part way through the season (Dec/Jan). How would you cut back the air? Partially cover the blower intake?
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Yes, I think there is a damper plate behind the blower motor where it screws to the door, slightly loosen the screws and slide the plate, use caution loosening the screws as they break very easily
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Thanks Sprinter - i understand the pv=mrt rule, but i'm not quite understanding what you're saying about my boiler. It's not pressurized so it should always be equal due to being open to atmosphere correct?
If you goto Calefi Idronics edition wood boilers they have diagrams of how you can achieve boiling under 212 degrees in an open system. I was referring to open systems, since we know increasing pressure raises the boiling point. Open systems are at risk of sub atmospheric conditions because they are not pressurized.
This is especially true when very large pumps are used, or when any part of the system is above the boiler water level. We understand siphoning right? Well when we pump water uphill it has to fall back down, thus creating a siphon or suction on the downhill side of loop. This suction creates all kinds of problems, sucking air in thru any air vents, valve packings, seals, etc. air can be the gurgling, or when the suction side goes sub atmospheric, ie. reduced pressure, you can get boiling in spots.
Another way is when a rediculously oversized circulator is used. Our pumps do not pump water at all, they circulate water by changing pressure on either side of the circulator. Water naturally wants to equalize, and this creates flow. Taco has a video showing this, and exactly how circulators work in hydronics. The circ itself can cause boiling, also all these OWB's usually have 1" ports, or let's say they have too small a port for the circ and pipe in the application. Well do we understand velocity stacks on carburetors, and the Bournoole principal. Shoving too much water too fast thru 1" pipe for instance creates positive pressure, now when it enters a large open volume of water there is a rapid change in pressure. Same for the supply side. Increasing circ speed would increase the issue and slowing it down by speed switch or valve would reduce the symptoms.
These are just some possibilities, you might have a hot spot, but that would have to be one very bad jacket design to do so. You would have to move much less than 4gpm through a 1" port to not disturb stratification layers in the boiler. If I had to bet, I'd look at other possibilities like mentioned above.
Just look up the threads I started with all the links to tons of hydronic info
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That makes sense - I did upgrade to a 1/2 Hp 3 speed grundphos this fall - perhaps it's causing the issue
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http://www.radiantandhydronics.com/articles/86249-noisy-pipes (http://www.radiantandhydronics.com/articles/86249-noisy-pipes)
Here's one option